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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kuz'menko A. M., Mukhin A. A., Ivanov V. Y., Kadomtseva A. M., Lebedev S. P., Bezmaternykh L. N.
Заглавие : Antiferromagnetic Resonance and Dielectric Properties of Rare-earth Ferroborates in the Submillimeter Frequency Range
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2011. - Vol. 113, Is. 1. - P113-120. - ISSN 1063-7761, DOI 10.1134/S106377611105013X
Примечания : Cited References: 27. - This work was supported by the Russian Foundation for Basic Research, project no. 10-02-00846.
Предметные рубрики: GDFE3(BO3)(4)
SPECTROSCOPY
CRYSTAL
Ключевые слова (''Своб.индексиров.''): antiferromagnetic resonance--basic parameters--effective anisotropy constant--ferroborates--ferroics--ferromagnetic orderings--frequency ranges--magnetic interactions--magnetoresonance--millimeter frequency range--rare earth ions--submillimeters--antiferromagnetic materials--crystallography--erbium--europium--ferromagnetic resonance--ion exchange--magnetic anisotropy--magnetic devices--magnetic structure--permittivity--resonance--antiferromagnetism
Аннотация: The magnetoresonance and dielectric properties of a number of crystals of a new family of multiferroics, namely, rare-earth ferroborates RFe(3)(BO(3))(4) (R = Y, Eu, Pr, Tb, Tb(0.25)Er(0.75)), are studied in the submillimeter frequency range (nu = 3-20 cm(-1)). Ferroborates with R = Y, Tb, and Eu exhibit permittivity jumps at temperatures of 375, 198, and 58 K, respectively, which are caused by the R32 - P3(1)2(1) phase transition. Antiferromagnetic resonance (AFMR) modes in the subsystem of Fe(3+) ions are detected in the range of antiferromagnetic ordering (T T(N)
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Pankrats A. I., Petrakovskii G. A., Bezmaternykh L. N., Bayukov O. A.
Заглавие : Antiferromagnetic resonance and phase diagrams of gadolinium ferroborate GdFe3(BO3)(4)
Разночтения заглавия :авие SCOPUS: Antiferromagnetic resonance and phase diagrams of gadolinium ferroborate GdFe3(BO3)4
Место публикации : J. Exp. Theor. Phys.: AMER INST PHYSICS, 2004. - Vol. 99, Is. 4. - P766-775. - ISSN 1063-7761, DOI 10.1134/1.1826168
Примечания : Cited References: 16
Ключевые слова (''Своб.индексиров.''): anisotropy--antiferromagnetic materials--antiferromagnetism--phase diagrams--resonance--single crystals--antiferromagnetic resonance--antiferromagnets--crystal axis--transition fields--gadolinium compounds
Аннотация: Antiferromagnetic resonance in single crystals of rhombohedral gadolinium ferroborate GdFe3(BO3)(4) was studied. The frequency-field dependences of antiferromagnetic resonance over the frequency range 26-70 GHz and the temperature dependences of resonance parameters for magnetic fields oriented along the crystal axis and in the basal plane were determined. It was found that the iron subsystem, which can be treated as a two-sublattice antiferromagnet with anisotropy of the easy-plane type, experienced ordering at T = 38 K. At temperatures below 20 K, the gadolinium subsystem with the opposite anisotropy sign strongly influenced the anisotropic properties of the crystal. This resulted in a spontaneous spin-reorientation transition from the easy-plane to the easy-axis state at 10 K. Below 10 K, magnetic field-induced transitions between the states were observed. Experimental phase diagrams on the temperature-magnetic field plane were constructed for fields oriented along the crystal axis and in the basal plane. A simple model was used to calculate the critical transition fields. The results were in close agreement with the experimental values measured at T = 4.2 K for both field orientations. (C) 2004 MAIK "Nauka / Interperiodica".
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kazak N. V., Belskaya N. A., Moshkina E. M., Bezmaternykh L. N., Vasiliev A. D., Sofronova S. N., Eremina R. M., Eremin E. V., Muftakhutdinov A. R., Cherosov M. A., Ovchinnikov S. G.
Заглавие : Antiferromagnetism of the cation-ordered warwickite system Mn2-xMgxBO4 (x=0.5, 0.6 and 0.7)
Коллективы : Russian Foundation for Basic ResearchRussian Foundation for Basic Research (RFBR) [20-02-00559]; Government of Krasnoyarsk Territory; Krasnoyarsk Regional Fund of Science to the research project [18-42243007]
Место публикации : J. Magn. Magn. Mater. - 2020. - Vol. 507. - Ст.166820. - ISSN 0304-8853, DOI 10.1016/j.jmmm.2020.166820. - ISSN 1873-4766(eISSN)
Примечания : Cited References: 39. - The reported study was funded by the Russian Foundation for Basic Research (no. 20-02-00559), Government of Krasnoyarsk Territory, Krasnoyarsk Regional Fund of Science to the research project. 18-42243007.
Предметные рубрики: SPIN-GLASS BEHAVIOR
CRYSTAL-STRUCTURES
SINGLE-CRYSTALS
INSIGHTS
MGFEBO4
Аннотация: X-ray diffraction, heat capacity and magnetic measurements are performed on single crystals of Mn2-xMgxBO4 (x = 0.5, 0.6 and 0.7) with the warwickite structure. The monoclinic symmetry is found for all samples with the space group P21/n. The M1 site is occupied by trivalent Mn ions while the M2 site is occupied by a mixture of divalent Mg and Mn ions. Regular cation and charge distributions are observed, which is unusual for heterometallic warwickites. The local octahedral distortions of M1O6 show the monotonic dependence on the Mg content and are in accordance with the Jahn-Teller distortion. All samples are found to undergo long-range antiferromagnetic ordering with rather low transition temperatures of TN = 16, 14 and 13 K for x = 0.5, 0.6, and 0.7, respectively. The ordering of local octahedral distortions, caused by the strong electron-phonon interaction of the trivalent Mn ions, is proposed to stabilise the cationic ordering and, as a result, the long-range magnetic ordering in the material.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Andryushin N. D., Zinenko V. I., Pavlovskii M. S., Shinkorenko A. S.
Заглавие : Calculation and Comparison of Electronic, Vibrational, Polarization, and Magnetic Properties of Double Perovskites CaMnTi2O6 and CaFeTi2O6
Место публикации : J. Exp. Theor. Phys. - 2019. - Vol. 129, Is. 6. - P.1036-1044. - ISSN 10637761 (ISSN), DOI 10.1134/S1063776119110013
Примечания : Cited References: 18. - This work was supported by the Russian Foundation for Basic Research (project no. 18-02-00130-a)
Аннотация: Vibrational, polarization, magnetic, and electronic properties of double perovskites CaMnTi2O6 and CaFeTi2O6 with a rare type of “column” ordering of divalent metal cations have been calculated based on the density functional theory. Analysis of the crystal lattice dynamics for paraelectric phase P42/nmc of both compounds has revealed that ferroelectric instability exists only in CaMnTi2O6. It is found that the structure distortion of the paraphrase of CaMnTi2O6 in the eigenvector of the unstable polar mode leads to a structure with the P42/nmc space group. The calculated spontaneous polarization for the ferroelectric phase of CaMnTi2O6 is Ps = 25 μC/cm2. The spin-polarization calculations have shown that the ground state is ferromagnetic in the CaFeTi2O6 crystal and antiferromagnetic in the CaMnTi2O6 crystal. The exchange interaction constants have been calculated using the Heisenberg model and the mean field approximation; the phase transition temperature for each compound has been estimated.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Golosovsky I. V., Vasilev A. I., Mukhin A. A., Ressouche E., Skumryev V., Urcelay-Olabarria I., Gudim I. A., Bezmaternykh L. N.
Заглавие : Complex magnetic order in the Nd(Tb)Fe3(BO3)4 multiferroic revealed by single-crystal neutron diffraction
Место публикации : Phys. Rev. B. - 2019. - Vol. 99, Is. 13. - Ст.134439. - ISSN 24699950 (ISSN) , DOI 10.1103/PhysRevB.99.134439
Примечания : Cited References: 33. - This work was supported by the Russian Grant No. RFBR 16-02-00058. A.A.M. acknowledges the financial support from the Russian Science Foundation (16-12-10531).
Аннотация: Magnetic structure of the substituted multiferroics-ferroborates Nd0.9Tb0.1Fe3(BO3)4 and Nd0.8Tb0.2Fe3(BO3)4 were determined in the framework of a self-consistent refinement of the single crystal neutron diffraction data. The small substitution of Nd for Tb leads to the reorientation of the main antiferromagnetic vector L from the basal plane towards the hexagonal axis. The reorientation takes place via an angular structure for which L does not coincide with the principal crystallographic directions and evolves with temperature due to competing magnetic anisotropies of Fe, Nd, and Tb subsystems. Our refinement at 2 K reveals the existence of distortions in the collinear antiferromagnetic Fe spin arrangement suggested before in other ferroborates. Therefore, besides the main antiferromagnetic vector L, the magnetic structure involves additional fine symmetrized combinations of spin components allowed by symmetry. They coexist with certain L components and could originate from the antisymmetric Dzyaloshinsky-Moriya Fe-Fe exchange interactions. At higher temperatures, the magnetic structure is described by the simple collinear model, where the L vector is deviated from the hexagonal plane. © 2019 American Physical Society.
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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Kuzmenko A. M., Mukhin A. A., Ivanov V.Yu., Bezmaternykh L. N.
Заглавие : Coupled R and Fe magnetic excitations in RFe 3(BO 3) 4 multiferroics
Коллективы : Moscow International Symposium on Magnetism
Место публикации : Diffusion and Defect Data Pt.B: Solid State Phenomena. - 2012. - Vol. 190. - P.269-272. - ISBN 9783037854365, DOI 10.4028/www.scientific.net/SSP.190.269
Ключевые слова (''Своб.индексиров.''): magnetic resonance--rare-earth iron borates--terahertz spectroscopy--antiferromagnetics--coupled mode--exchange coupled--frequency ranges--g factors--iron borate--magnetic excitations--multiferroics--resonance mode--strong interaction--transmission spectrums--antiferromagnetism--electron transitions--gadolinium--ions--magnetic materials--magnetic permeability--magnetic resonance--terahertz spectroscopy--neodymium
Аннотация: Various resonance modes were observed in the transmission spectra of rare-earth iron borates RFe 3(BO 3) 4 (R = Nd 3+, Sm 3+, Gd 3+) at the frequency range 100-600 GHz, which were attributed to collective magnetic excitations in the exchange coupled Fe- and R-subsystems, i.e. antiferromagnetic (Fe) resonance and electron transitions in the R-ions. Strong interaction of the Fe and R oscillations was revealed and theoretically analyzed taking into account feature of the R-ion ground state. Intensities of the coupled modes (contributions to magnetic permeability) strongly depend on a difference of Fe and R ions g-factors that allows defining the sign of the latter. In particular, an appreciable intensity of exchange (Nd) modes in NdFe 3(BO 3) 4 is caused by g Nd?,|| < 0 whereas in GdFe 3(BO 3) 4 with gGd ? gFe ? 2 the exchange (Gd) modes were hided due to compensation of Fe and Gd contributions. In SmFe 3(BO 3) 4, despite a negligible Sm g-factor, the Sm modes were clear observed due to their excitation via coupling with the Fe-subsystem. В© (2012) Trans Tech Publications.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kulbakov A. A., Sarkar R., Janson O., Dengre S., Weinhold T., Moshkina E. M., Portnichenko P. Y., Luetkens H., Yokaichiya F., Sukhanov A. S., Eremina R. M., Schlender P., Schneidewind A., Klauss H. -H., Inosov D. S.
Заглавие : Destruction of long-range magnetic order in an external magnetic field and the associated spin dynamics in Cu2GaBO5 and Cu2AlBO5 ludwigites
Место публикации : Phys. Rev. B. - 2021. - Vol. 103, Is. 2. - Ст.024447. - ISSN 24699950 (ISSN), DOI 10.1103/PhysRevB.103.024447
Примечания : Cited References: 46. - We thank U. Nitzsche for technical assistance. This project was funded in part by the German Research Foundation (DFG) under Grant IN 209/9-1, via Project C03 of the Collaborative Research Center SFB 1143 (project-id 247310070) at the TU Dresden, and the Würzburg-Dresden Cluster of Excellence on Complexity and Topology in Quantum Matter—ct.qmat (EXC 2147, project-id 390858490). O.J. was supported by the Leibniz Association through the Leibniz Competition
Аннотация: The quantum spin systems Cu2M′BO5 (M′=Al,Ga) with the ludwigite crystal structure consist of a structurally ordered Cu2+ sublattice in the form of three-leg ladders, interpenetrated by a structurally disordered sublattice with a statistically random site occupation by magnetic Cu2+ and nonmagnetic Ga3+ or Al3+ ions. A microscopic analysis based on density-functional-theory calculations for Cu2GaBO5 reveals a frustrated quasi-two-dimensional spin model featuring five inequivalent antiferromagnetic exchanges. A broad low-temperature 11B nuclear magnetic resonance points to a considerable spin disorder in the system. In zero magnetic field, antiferromagnetic order sets in below TN≈4.1 K and ∼2.4 K for the Ga and Al compounds, respectively. From neutron diffraction, we find that the magnetic propagation vector in Cu2GaBO5 is commensurate and lies on the Brillouin-zone boundary in the (H0L) plane, qm=(0.45,0,−0.7), corresponding to a complex noncollinear long-range ordered structure with a large magnetic unit cell. Muon spin relaxation is monotonic, consisting of a fast static component typical for complex noncollinear spin systems and a slow dynamic component originating from the relaxation on low-energy spin fluctuations. Gapless spin dynamics in the form of a diffuse quasielastic peak is also evidenced by inelastic neutron scattering. Most remarkably, application of a magnetic field above 1 T destroys the static long-range order, which is manifested in the gradual broadening of the magnetic Bragg peaks. We argue that such a crossover from a magnetically long-range ordered state to a spin-glass regime may result from orphan spins on the structurally disordered magnetic sublattice, which are polarized in magnetic field and thus act as a tuning knob for field-controlled magnetic disorder.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Korshunov M. M., Gavrichkov V. A., Ovchinnikov S. G., Nekrasov I. A., Kokorina E. E., Pchelkina Z. V.
Заглавие : Dominance of many-body effects over the one-electron mechanism for band structure doping dependence in Nd2-xCexCuO4: the LDA + GTB approach
Разночтения заглавия :авие SCOPUS: Dominance of many-body effects over the one-electron mechanism for band structure doping dependence in Nd2-xCexCuO4: The LDA+GTB approach
Место публикации : J. Phys.: Condens. Matter: IOP PUBLISHING LTD, 2007. - Vol. 19, Is. 48. - Ст.486203. - ISSN 0953-8984, DOI 10.1088/0953-8984/19/48/486203
Примечания : Cited References: 36
Предметные рубрики: NARROW ENERGY BANDS
HUBBARD-MODEL
SUPERCONDUCTORS
DENSITY
TEMPERATURE
ORBITALS
WAVE
Ключевые слова (''Своб.индексиров.''): antiferromagnetism--band structure--correlation methods--crystal structure--local density approximation--superconducting materials--electronic correlations--fermionic quasiparticles--neodymium compounds
Аннотация: In the present work we report band structure calculations for the high-temperature superconductor Nd2-xCexCuO4 in the regime of strong electronic correlations within an LDA + GTB method, which combines the local density approximation (LDA) and the generalized tight-binding method (GTB). The two mechanisms of band structure doping dependence were taken into account. Namely, the one-electron mechanism provided by the doping dependence of the crystal structure, and the many-body mechanism provided by the strong renormalization of the fermionic quasiparticles due to the large on-site Coulomb repulsion. We have shown that, in the antiferromagnetic and in the strongly correlated paramagnetic phases of the underdoped cuprates, the main contribution to the doping evolution of the band structure and Fermi surface comes from the many-body mechanism.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ovchinnikov S. G., Korshunov M. M., Shneyder E. I.
Заглавие : Effect of short antiferromagnetic correlations on the normal and superconducting properties in copper oxides
Место публикации : Diffusion and Defect Data Pt.B: Solid State Phenomena: Trans Tech Publications Ltd, 2011. - Vol. 168-169. - С. 561-566. - ISSN 10120394 (ISSN); 9783037850213 (ISBN), DOI 10.4028/www.scientific.net/SSP.168-169.561
Ключевые слова (''Своб.индексиров.''): high temperature superconductivity--short range antiferromagnetic order--strong electron correlations--antiferromagnetic materials--antiferromagnetism--copper oxides--electron correlations--electron density measurement--antiferromagnetism--electron correlations--ab initio--antiferromagnetic correlations--cuprates--high-t--high-temperature superconductivity--hubbard--low energies--multiband model--short range antiferromagnetic order--strong electron correlations--superconducting properties--t-j models--antiferromagnetic orderings--superconductivity--copper oxides--high temperature superconductivity
Аннотация: The abnormal "normal" state and origin of high temperature superconductivity in cuprates are still not clear [1-2]. The strong electron correlations (SEC) are known to be one of the main difficulties for the theory of high- Tc cuprates. The conventional LDA (local density approximation) approach to the band structure fails in the regime of SEC. Various realistic multiband models of a CuO2 layer at low energy result in the effective Hubbard or t - J models [3-7]. The hybrid LDA+GTB scheme [8] generates the low-energy effective t - t? - t? - J* model with all parameters calculated ab initio.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Val'kov V. V., Aksenov S.V.
Заглавие : Effects of inelastic spin-dependent electron transport through a spin nanostructure in a magnetic field
Место публикации : J. Exp. Theor. Phys. - NEW YORK: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2011. - Vol. 113, Is. 2. - С. 266-275. - AUG. - ISSN 1063-7761, DOI 10.1134/S1063776111060070
Примечания : Cited Reference Count: 30. - Гранты: This study was carried out under the program of the Physical Science Department of the Russian Academy of Sciences, Federal Target Program "Scientific and Scientific-Pedagogical Personnel of Innovative Russia in 2009-2013," Interdisciplinary Integration project no. 53 of the Siberian Branch of the Russian Academy of Sciences, and under partial support from the Russian Foundation for Basic Research (project no. 09-02-00127). The research work of one of the authors (S.V.A) was supported by grant no. MK-1300.2011.2 from the President of the Russian Federation.Финансирующая организация: Russian Foundation for Basic Research [09-02-00127]; Russian Federation [MK-1300.2011.2]
Предметные рубрики: CONDUCTION
ANISOTROPY
JUNCTIONS
Ключевые слова (''Своб.индексиров.''): antiferromagnetic coupling--colossal magnetoresistance effect--iv characteristics--metallic contacts--potential profiles--spectral characteristics--spin dependent transport--spin dimer--spin moments--spin-dependent electron transport--spin-flip process--tight-binding approximations--transmission coefficients--antiferromagnetism--colossal magnetoresistance--current voltage characteristics--electric resistance--nanostructures--transport properties--magnetic field effects
Аннотация: The transport properties and current-voltage (I-V) characteristics of a system of spin dimers with antiferromagnetic coupling arranged between metallic contacts are investigated in the tight binding approximation using the Landauer-Buttiker formalism. It is shown that the s-d(f) exchange interaction between the spin moments of the electrons being transported and the spins of the nanostructure leads to the formation of a potential profile as well as its variation due to spin-flip processes. As a result, the spin-dependent transport becomes inelastic, and the transmission coefficient and the I-V characteristic are strongly modified. It is found that the application of a magnetic field induces additional transparency peaks in the spectral characteristic of the system and causes the colossal magnetoresistance effect.
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Orlov Yu. S., Nikolaev S. V., Gavrichkov V. A., Ovchinnikov S. G.
Заглавие : Exchange interaction between the high spin Co3+ states in LaCoO3
Место публикации : Comput. Mater. Sci. - 2022. - Vol. 204. - Ст.111134. - ISSN 09270256 (ISSN), DOI 10.1016/j.commatsci.2021.111134
Примечания : Cited References: 59. - We are thankful to the Russian Science Foundation, Russia for the financial support under the project 18-12-00022
Аннотация: The formation of the exchange interaction between HS Co3+ ions, which are excited in LaCoO3, is studied within the multielectron approach. Two main contributions appear to be antiferromagnetic (AFM) and ferromagnetic (FM). When the ground state is LS, the total interaction is AFM. The crossover to the HS state may result in the FM ordering. The mean-field magnetic phase diagrams on the plane spin gap-temperature have been calculated without and with spin-orbital interaction in the HS term. Without spin-orbital interaction the reentrant magnetic order is possible. The spin-orbital coupling removes the reentrant phase transition and stabilizes the LS state. For known from experimental data values of the spin gap and exchange interaction, the ideal stoichiometric LaCoO3 is very close to the LS–HS crossover and magnetic ordering border. The violations of local coordination and symmetry of the Co3+-oxygen complexes that take place in the intergrain boundaries, at the surface of single crystals, and in the thin films on the strained substrate, may result in the formation of the HS state and FM order for such materials.
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Orlov Yu. S., Nikolaev S. V., Dudnikov V. A., Gavrichkov V. A., Ovchinnikov S. G.
Заглавие : Features of spin crossovers in magnetic materials
Колич.характеристики :26 с
Место публикации : Phys. Usp. - 2023. - Vol. 66, Is. 7. - P.647-672. - ISSN 10637869 (ISSN), DOI 10.3367/UFNe.2022.05.039195. - ISSN 14684780 (eISSN)
Примечания : Cited References: 237. - The authors thank the Russian Science Foundation for financial support in the framework of project no. 18-12-00022
Аннотация: We present experimental and theoetical results of spin crossover studies in magnetically ordered materials. The effect of spin crossovers on the electronic structure of transition metal oxides and on the Bose condensation of spin excitons in the vicinity of the spin crossover is considered. A new method for calculating the interatomic superexchange interaction in transition metal oxides is discussed that allows considering selective contributions of excited magnetic cation terms. Changes in the exchange interaction sign are predicted for spin crossovers for d5—d7 ions. In the RCoO3 family of rare-earth cobaltites, the ground state is nonmagnetic, but, as the temperature increases, thermal excitations of high-spin states give rise to a number of experimentally detectable features. In defective RCoO3 samples, stabilization of the high-spin term and ferromagnetic ordering are possible. Dynamical crossovers under external pumping and the dynamics of multiplicity, magnetization, and local lattice distortions are discussed. Geophysical implications of spin crossovers are considered, and metallic properties of Earth's mantle at a depth of 1400—1800 km are predicted.
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Roessli B., Schefer J., Petrakovskii G. A., Ouladdiaf B., Boehm M., Staub U., Vorotinov A. M., Bezmaternikh L. N.
Заглавие : Formation of a magnetic soliton lattice in copper metaborate
Место публикации : Phys. Rev. Lett.: AMERICAN PHYSICAL SOC, 2001. - Vol. 86, Is. 9. - P1885-1888. - ISSN 0031-9007, DOI 10.1103/PhysRevLett.86.1885
Примечания : Cited References: 26
Предметные рубрики: SPIN-WAVES
BA2CUGE2O7
TRANSITION
ANTIFERROMAGNET
CUGEO3
PHASE
Ключевые слова (''Своб.индексиров.''): anisotropy--antiferromagnetism--ground state--magnetic moments--magnetic properties--magnetization--neutron diffraction--neutron scattering--phase transitions--solitons--thermal effects--antiferromagnetic state--copper metaborate--higher order magnetic satellites--magnetic soliton lattice--magnetic structure--copper compounds
Аннотация: The magnetic ground state of CuB2O4 is incommensurate at T = 1.8 K and undergoes a continuous phase transition to a noncollinear commensurate antiferromagnetic state at T* similar to 10 K. Close to T* higher-order magnetic satellites are observed. Coexistence of long- and short-range magnetic order is observed in both magnetic phases. This suggests that the association of the Dzyaloshinskii-Moriya interaction and anisotropy leads to the formation of a magnetic soliton lattice.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Orlov Yu. S., Nikolaev S. V., Dudnikov V. A., Ovchinnikov S. G.
Заглавие : Forming a dielectric exciton phase in strongly correlated systems with spin crossover
Место публикации : Phys. Rev. B. - 2021. - Vol. 104, Is. 19. - Ст.195103. - ISSN 24699950 (ISSN), DOI 10.1103/PhysRevB.104.195103
Примечания : Cited References: 46. - The authors thank the Russian Scientific Foundation for financial support under Grant No. 18-12-00022
Аннотация: Formation of the magnetic structure and exciton condensate of local magnetic excitons in strongly correlated systems near the spin crossover under high pressure is considered in terms of the effective Hamiltonian obtained from a two-band Hubbard model in the regime of strong electron correlations. The coexistence of the long-range antiferromagnetic order and exciton condensate and the occurrence of the magnetization caused by the condensation of local magnetic excitons are demonstrated. Transformation of the electronic structure of the antiferromagnetic high-spin insulator into the paramagnetic two-band correlated metal via a narrow-gap antiferromagnetic excitonic semiconductor is obtained.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gavrichkov V. A., Polukeev S. I., Ovchinnikov S. G.
Заглавие : Superexchange interaction in magnetic insulators with spin crossover
Место публикации : J. Exp. Theor. Phys. - 2018. - Vol. 127, Is. 4. - P.713-720. - ISSN 10637761 (ISSN), DOI 10.1134/S1063776118100023
Примечания : Cited References: 34. - This work was supported by the Russian Science Foundation (project no. 18-12-00022).
Ключевые слова (''Своб.индексиров.''): antiferromagnetism--ground state--high pressure engineering--ions--iron compounds--magnetic materials
Аннотация: We present the derivation of a microscopic superexchange Hamiltonian for undoped magnetic insulators with an arbitrary spin. It is established that the sign of the (ferromagnetic or antiferromagnetic) superexchange between magnetic ions in the dn configuration depends on the spin nature of virtual multielectron states dn± 1, viz., low-spin or high-spin partners with S ± 1/2 relative to ground state of the dn configuration with spin S. A macroscopic substantiation is given for the Goodenough–Kanamori rules and simple mean-field estimates connecting the magnetic ordering temperature with the exchange constant. The conventional Anderson superexchange for magnetic materials with spin S = 1/2 and the P/T magnetic phase diagram for ferroborate FeBO3 with spin crossover S = (5/2 ↔ 1/2) at the Fe3+ ion under a high pressure are also reproduced as a test.
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Volkov N. V., Sablina K. A., Eremin E. V., Boni P., Shah V. R., Flerov I. N., Kartashev A., Rasch JCE, Boehm M., Schefer J.
Заглавие : Heat capacity of a mixed-valence manganese oxide Pb(3)Mn(7)O(15)
Коллективы :
Разночтения заглавия :авие SCOPUS: Heat capacity of a mixed-valence manganese oxide Pb3Mn 7O15
Место публикации : J. Phys.: Condens. Matter: IOP PUBLISHING LTD, 2008. - Vol. 20, Is. 44. - Ст.445214. - ISSN 0953-8984, DOI 10.1088/0953-8984/20/44/445214
Примечания : Cited References: 11. - This study was supported by the INTAS (project No 061000013-9002), the Division of Physical Sciences of RAS, program `Spin-dependent Effects in Solids and Spintronics' (project No. 2.4.2 of SB RAS), the President of the Russian Federation, grant for Support of Leading Scientific Schools (project No. NSh-1011.2008.2), KRSF-RFBR `Enisey2007', project No. 07-02-96801-a, and the Siberian Branch of RAS, Integration project No. 3.7.
Ключевые слова (''Своб.индексиров.''): antiferromagnetism--crystallography--entropy--lead alloys--magnetic materials--magnetism--manganese--manganese compounds--powders--single crystals--specific heat--spin dynamics--antiferromagnetic orders--charge localizations--entropy losses--excess heat capacities--experimental datums--heat capacities--magnetic contributions--magnetic orders--magnetic states--magnetic subsystems--magnetic transitions--manganese oxides--nonmagnetic--spin systems--temperature curves--temperature dependences--temperature intervals--temperature ranges--manganese alloys
Аннотация: We present the results of a heat capacity study of Pb(3)Mn(7)O(15) single crystals with approximately equal concentrations of Mn(3+) and Mn(4+) ions. In the temperature interval between 210 and 260 K, an excess heat capacity of nonmagnetic origin, most likely associated with the process of charge localization, has been observed. Also, three pronounced anomalies corresponding to the changes in a magnetic subsystem of the crystal have been observed in the temperature dependence of the heat capacity. A broad hump near 150 K is related to the formation of a short-range magnetic order. This process of short-range ordering is rather prominent, considering the appreciable value of the entropy loss accompanying the change in the magnetic state. A clear lambda-shaped peak at 70 K marks the onset of a long-range antiferromagnetic order. Another anomalous contribution to the heat capacity of magnetic origin has been revealed at temperatures below 20 K. This contribution is associated with a magnetic transition of an unknown nature, which is also clearly evident in magnetization versus temperature curves. The total magnetic contribution to the entropy deduced from the actual experimental data over the entire temperature range is much smaller than is expected for a completely ordered Mn spin system in the crystal. We suggest several possible reasons that may account for this `missing' entropy.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aplesnin S. S., Petrakovskii G. A., Ryabinkina L. I., Abramova G. M., Kiselev N. I., Romanova O. B.
Заглавие : Influence of magnetic ordering on the resistivity anisotropy of alpha-MnS single crystal
Разночтения заглавия :авие SCOPUS: Influence of magnetic ordering on the resistivity anisotropy of α-MnS single crystal; авие SCOPUS: Influence of magnetic ordering on the resistivity anisotropy of ?-MnS single crystal
Место публикации : Solid State Commun.: PERGAMON-ELSEVIER SCIENCE LTD, 2004. - Vol. 129, Is. 3. - P195-197. - ISSN 0038-1098, DOI 10.1016/j.ssc.2003.09.028; Solid State Commun. - 2004. - Vol. 129, Is. 3. - P195-197. - Вариант Sopus
Примечания : Cited References: 7
Ключевые слова (''Своб.индексиров.''): anisotropy of resistivity--optical gap--d. anisotropy of resistivity--d. optical gap--antiferromagnetism--band structure--bandwidth--diffractometers--electron transitions--fermi level--hamiltonians--light absorption--magnetic anisotropy--magnetization--single crystals--spectroscopic analysis--x ray diffraction analysis--coulomb repulsion--resistivity anisotropy--semiconducting manganese compounds--d. anisotropy of resistivity--d. optical gap--antiferromagnetism--band structure--bandwidth--diffractometers--electron transitions--fermi level--hamiltonians--light absorption--magnetic anisotropy--magnetization--single crystals--spectroscopic analysis--x ray diffraction analysis--coulomb repulsion--resistivity anisotropy--semiconducting manganese compounds
Аннотация: The resistivity and the optical absorbtion spectra of single crystal alpha-MnS are studied in the temperature range 80-300 K along two directions [100] and [111]. Strong anisotropy of the resistivity, and the shift of absorbtion spectra band edge below T 160 K are explained in terms of model involving delocalized holes in 3d-band manganese ions interacting with localized spins by using the sd-model. (C) 2003 Elsevier Ltd. All rights reserved.
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Eremina R. M., Moshkina E. M., Gavrilova T. P., Muftakhutdinov A. R., Gilmutdinov I. F.
Заглавие : Investigation of the Magnetic Properties of Warwickite Mn0.89Mg1.11BO4
Место публикации : Bull. Russ. Acad. Sci. Phys. - 2019. - Vol. 83, Is. 7. - P.792-794. - ISSN 10628738 (ISSN), DOI 10.3103/S106287381907013X
Примечания : Cited References: 3. - This work was supported by the Russian Foundation for Basic Research; the Administration of Krasnoyarsk Krai; and the Krasnoyarsk Krai Science Foundation, project no. 18-42-243007.
Аннотация: The temperature dependences of the magnetic susceptibility in magnetic fields applied parallel and perpendicular to axis с of a Mn0.89Mg1.11BO4 single crystal were measured. Spin ordering typical of an antiferromagnetic with an easy magnetization axis was observed below 16 K. The Dzyaloshinskii–Moriya interaction between spins of manganese ions in Mn0.89Mg1.11BO4 was estimated by analyzing the EPR linewidth. © 2019, Allerton Press, Inc.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Korshunov M. M., Ovchinnikov S. G., Sherman A. V.
Заглавие : Effective Hamiltonian and the properties of normal and superconductive phases of n-type cuprates
Место публикации : Physica B: ELSEVIER SCIENCE BV, 2005. - Vol. 359: International Conference on Strongly Correlated Electron Systems (SCES 04) (JUL 26-30, 2004, Karlsruhe, GERMANY). - P521-523. - ISSN 0921-4526, DOI 10.1016/j.physb.2005.01.134
Примечания : Cited References: 13
Предметные рубрики: MODEL
SYMMETRY
Ключевые слова (''Своб.индексиров.''): strong electron correlations--superconductivity--multiband p-d model--n-type cuprates--multiband p-d model--n-type cuprates--strong electron correlations--superconductivity--antiferromagnetism--correlation theory--fermi surface--hamiltonians--mathematical models--microscopic examination--oxide superconductors--phase diagrams--semiconductor doping--generalized tight-binding (gtb)--multiband p-d models--n-type cuprates--single electron correlations--superconductivity
Аннотация: In the framework of the effective low-energy model for high-T-c, cuprates with account for three-center interaction terms and spin fluctuations the properties of normal and superconducting phases of n-type cuprates are investigated. Microscopic model parameters were obtained from ARPES data in undoped compounds. Obtained evolution of the chemical potential with doping, Fermi surface at optimal doping, and T-c(x) phase diagram are in remarkably good agreement with the experiment. (c) 2005 Elsevier B.V. All rights reserved.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kuz'min E. V., Ovchinnikov S. G., Singh D. J.
Заглавие : Effect of frustrations on magnetism in the Ru double perovskite Sr2YRuO6
Место публикации : Phys. Rev. B: AMERICAN PHYSICAL SOC, 2003. - Vol. 68, Is. 2. - Ст.24409. - ISSN 1098-0121, DOI 10.1103/PhysRevB.68.024409
Примечания : Cited References: 24
Предметные рубрики: MOTT TRANSITION
LATTICE
SPIN
ANTIFERROMAGNETISM
SUPERCONDUCTIVITY
FERROMAGNETISM
Аннотация: Localized Ru5+ spins in Sr2YRuO6 form a fcc lattice with an antiferromagnetic (AFM) nearest-neighbor (NN) coupling J approximate to 25 meV and rather low Neel temperature T-N= 26 K. Analysis of the electronic structure of Sr2RuO4 results in the effective Heisenberg model. We have studied the effect of frustrations on the AFM type-I structure of Sr2YRuO6 in the spin-wave approximation. In the model with only NN coupling the AFM state is unstable due to frustrations, and T-N = 0. Stabilization of the AFM state occurs due to the next-nearest-neighbor coupling I or due to the magnetic anisotropy D. Very small values D/J similar to I/J less than or equal to 10(-3) are enough to obtain the experimental values of T-N and sublattice magnetization m = 1.85 mu(B) /Ru (62% from the nominal S = 3/2 value).
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